Motor fuels



Patented Oct. 8, 1946 MOTOR FUELS Preston L. Veltman, Port Arthur, 'Tex., assig'nor to Texaco Development Corporation, Jersey City. N. 3., a corporation of Delaware No Drawing.

bonyl compounds have shown promising antiknock characteristics, especially the carbonyl compounds of iron, nickel, and cobalt. These compounds, however, have been found to be very unstable to the effects of light and oxygen, and to be undesirable in view 'of their very high v01- atility, resulting in handling difficulties and explosion hazards. Thus, in spite of the fact that their anti-knock properties have been known for a number of years, these metal carbonyls are not utilized in the commercial production of motor fuels.

I have now found that metal carbonyl derivatives of greatly improved light stability can be prepared by reacting the metal carbonyls with unsaturated hydrocarbons, and that the resulting reaction products are very satisfactory antiknock agents for motor fuels, and are free from other undesirable characteristics of the metal carbonyls, per se.

I have further found that these reaction products are especially advantageous for the production of fuels suitable for obtaining high power output from supercharged engines. Motor fuels containing my improved anti-knock agents are particularly adapted for use in super-rich mixtures, i. e., at air-fuel ratios of less than 11/1, These fuels, therefore, are very desirable for obtaining maximum power output, without detonation, in supercharged engines, especially in engines of high speed, high heat load types, such as the air-cooled, supercharged aircraft engines. This special utility of the fuels containing the present anti-knock agents constitutes an important phase of my invention.

The metal carbonyl reaction products which I have found to be suitable for use as anti-knock agents, may be prepared by the reaction of unsaturated hydrocarbons with 'carbonyls of metals of the eighth group of the erio di'cjtable, and especially the various "carbonyls of the metals of Application July 1'7, 1942, Serial No. 451,324

14 Claims.

2 atomic numbers 28 to 28, i. e., iron, nickel, and cobalt. Suitable unsaturated hydrocarbons for this reaction are the olefins, .diolefins, aromatic hydrocarbons, and alkyl or alkylene substituted aromatic hydrocarbons. The desired reaction products, which are also referred to herein as complexes, may generally be prepared by react-:- ing the metal carbonyl and the unsaturated -hy drocarbon in the liquid phase at elevated temperatures and elevated pressures. ;A suitable procedure, in most cases, comprises the reaction of the metal .pentacarbonyl with the unsaturated hydrocarbon attemperatures of -300 F. under the vapor pressure of the reaction mixture. A The reaction products of the metal carbonyls and the unsaturated hydrocarbons are believed to be true complexes, or coordination compounds, and the colored nature of the products is evi: dence in support of this belief. Attempts have been made to assign definite formulas to the reaction products of iron .pentacarbonyl with 1,3-

butadiene, 2-methylbutadiene-1,3, and 2;,3-dig- .methylbutadiene-lfi (Reihlen et al., Ann. 482 161). However, the indefinite boiling points of the products, and the difliculties of analyses have made it impossible thus far to determine with certainty whether the the reaction productsare true complexes of definite constitution. I have found, for example, that the reaction product of iron pentacarbonyl and 1,3-butadie'ne, may be separated into fractions of somewhat different boiling ranges, which may indicate thata number of different complexes were formed, 'orthat there is no complex of fixed constitution in the reaction product. However, I have found that all of the fractions thus 'separated'hav'e antiknock characteristics and are useful in the pres"- ent invention. It is to be understood, therefore, that my invention relates to the reaction products of unsaturated hydrocarbons with metal carbonyls of the above class, irrespective of the molecular constitution of such. reaction prod"- ucts.

The metal carbonyl reaction product may be incorporated in any of the usual types of fuels for internal combustion engines, such as straight run gasolines, thermally or catalytically cracked gasolines, alkylation gasolines, thermally or catalytically reformed or hydroformedgasolines, and various blends of such-fuels. However, thegreatest utility of these anti-knock agents is in the production of fuels of high power output in super-rich mixture operation of supercharged engines. For this purpose, the base fuel, to which the anti-knock agent is to be added, may suitably be chosen on the basis of its lean mixture performance, and fuels containing a relatively high proportion of 2,2,4-trimethylpentane (isooctane), are especialy suitable from this standpoint. The base fuels may also contain antiknock agents such as tetra-ethyl lead, or materials such as aromatic hydrocarbons which also improve the performance of the fuels in superrieh mixtures. Blends of aromatic hydrocarbons, or hydroformed gasolines, with straight run gasolines or alkylation gasolines, constitute suitable base stocks for the preparation of fuels having superior performance in super-rich mixtures. The addition of metal carbonyl reaction products to such base stocks produces fuels capable of maximum power output in supercharged engines which cannot be equalled by combinations of isooctane and tetra-ethyl lead, without exceeding the limit of lead concentration now believed to be safe.

The amount of the metal carbonyl-unsaturated hydrocarbon reaction product to be incorporated in any base stock will, of course, depend upon the anti-knock characteristics of the base stock itself and the desired characteristics of the fuel to be produced. Any measurable amount of a metal carbonyl reaction product will have a measurable effect upon the anti-knock characteristics of the fuel, and there appears to be no upper limit to the amount which canbe incorporated, other than that fixed by economic considerations. For most purposes, however, concentrations of the anti-knock agent ranging from 0.1 to ml. per gallon of fuel will be satisfactory, and amounts from 1 to 6 ml. per gallon of fuel will meet most requirements with base stocks of the present types. I generally prefer to use concentrations corresponding to 0.15 g. to 1.5 g. of metal per gallon of fuel.

It is to be understood that the anti-knock agents of the present invention may be used in conjunction with other known anti-knock agents, such as tetra-ethyl lead, and that the fuels containing my anti-knock agents may also contain other common fuel additives, such as dyes, gum inhibitors, stabilizing agents, and agents for insuring the removal from the engines of metal residues of the anti-knock compounds.

The motor fuels containing my improved antiknock agents are suitable for use in all types of spark ignition, internal combustion engin es, and such fuels may be used as a single fuel source or as an auxiliary fuel for operation under conditions requiring a fuel of high anti-knock quality. Alternatively, my anti-knock agents may be used in conjunction with a base fuel containing no anti-knock agent, or containin an anti-knock agent of different characteristics, and may be injected into the fuel supply, or into the engine, only when operating conditions demand additional knock suppression. This latter use is especially applicable to full throttle operation of supercharged engines, as in the operation of aircraft engines during take-off or steep climb. In-suchoperation, the engine may suitably be provided with an auxiliary supply of the metal carbony1 complex during full throttle operation, while maintaining theair-fuel ratio below 11/1, and preferably at the optimum power output ratio for the particular combination of base fuel and metal carbonyl reaction product.

It is to be understood that the methods discussed above are merely illustrative, and that any equivalent procedures may be employed for taking advantage of the special properties of my anti-knock agents.

My invention will be further illustrated by the following specific examples:

Example I Liquid 1,3-butadiene and liquid iron pentacarbonyl, in a ratio of approximately 1.6 mols of butadiene per mol of iron carbonyl, were introduced into a pressure reaction vessel in which the air had been displaced by nitrogen. The vessel was then sealed and slowly heated to a temperature of approximately 215 F. The temperature was then maintained at -215 F. for 24 hrs., after which the vessel was cooled and the reaction mixture withdrawn. The unreacted butadiene was distilled ofi at room temperature, leaving a yellow liquid reaction product. This material was subjected to vacuum distillation, and a fraction was obtained at 122 F. (10 mm.), which corresponded closely in analysis to [FB(CO)3]5'[C4H6]6 The fraction described above was incorporated in a 300 F. end point alkylation gasoline obtained by the sulfuric acid alkylation of isobutane with butylenes. The concentration of the iron carbonyl complex in the fuel was 2.0 ml. per gallon, corresponding to approximately 5.56 g. of Fe per gallon. The resulting fuel was tested in a supercharged engine in accordance with the AFB-3C test method, and it was found that the maximum allowable indicated mean effective pressure (IMEP) was approximately 163 lbs/sq. in. at an air-fuel ratio of 8.5/1. In a comparable test in the same engine this alkylation gasoline, without the addition of the iron carbonyl complex, produced a maximum allowable IMEP of only approximately 138 lbs./sq. in.

It may be seen that the use of the iron carbony1 complex thus increased, by nearly 12 per cent, the maximum permissible power output from the test engine when employing this alkylation gasoline as the base fuel.

Example [I The procedure of Example I was followed for the production of an iron carbonyl-di-isobutylene complex, using liquid di-isobutylene and liquid iron pentacarbonyl in a ratio of approximately 1.9 mols of di-isobutylene per mol of iron pentacarbonyl. Vacuum distillation of the product yielded a fraction boiling at 82-84 F. (56-63 mm.), which was a stable yellow liquid having iron, carbon and lwdrogen analyses corresponding closely to the formula [Fe(CO)5la-[CaH1s]5. This material was incorporated in a 300 F. end point alkylation gasoline, obtained by the sulfuric acid alkylation of isobutane with butylenes, in a concentration corresponding to approximately 0.27 g. Fe per gallon. The resulting fuel was tested in a supercharged engine in accordance with the AFD-3C test method, and was found to produce a maximum allowable IMEP of approximately 142 lbs/sq. in at an air-fuel ratio of 8/1. In a comparable test in the same engine, this alkylation gasoline without the iron carbony1 complex produced a maximum allowable IMEP of approximately 134 lbs/sq. in.

Example III A fuel consisting of 60 percent by volume of 300 F. end point alkylation gasoline of the type previously described and 40 per cent by volume of ethylbenzene was tested in a supercharged enlue in accordance with the AFB-3C test methd, and the maximum allowable IMEP was found to be approximately 206 lbs/sq. in. at an air-fuel ratio of '7/ 1. The same fuel with the addition of 0.28 g. Fe per gallon, in the form of a complex corresponding closely to [Fe(CO)]3' [C8H1615, produced a maximum allowable IMEP of 237 lbs/sq. in. at an air-fuel ratio of approximately 7/1.

The two fuel described above were again tested, with the further addition of tetra-ethyl lead. The maximum allowable IMEP in each case is shown in the following table:

Concentrallliiixifllglln ion, g. a owa e Addmve metal/gal. IMEP, 1bs./

fuel sq. in.

Example IV Th base fuels of Examples II and III, and these fuels with added iron pentacarbonyldiisobutylene complex, as described in these examples, were tested by the CFRM method. The octane values found in each case are shown in the table below:

Concentration of CFRM Fuel O)t]a'[CsHm]5 octane g. Felgal. N o.

Alkylation gasoline 0. 00 91. 3 e0 fir-ite? a y a iongaso e, 0 yrsnzcne l 0.00 91. 7 alkylation gasoline, 40% ethylenzene 0. 28 95. 4

The fuel blends of the above examples were tested shortly after preparation, as a safeguard against possible instability of the iron carbonyl complexes when dissolved in these base fuels.

Although the metal carbonyl complexes are much examples are merely illustrative, and do not limit the scope of my invention. A has been previously pointed out, other metal carbonyl complexes of the class defined above may be substituted for the particular iron pentacarbony1 reaction prodducts used in these examples; and the motor fuels may be otherwise modified in accordance with prior practices in the art. In general, it may be said that the use of any equivalents, or modifications which would naturally occur to one skilled in the art, is included in the scope of the present invention. Only such limitations should be imposed on the scope of my invention as are indicated in the appended claims.

I claim:

1. A motor fuel comprising a hydrocarbon base fuel having dissolved therein a minor amount of an organo-metallic anti-knock agent comprising essentially a product obtained by heating together under pressure an unsaturated hydrocarbon and a carbonyl of a metal of atomic number 26 to 28.

2 A motor fuel comprising a hydrocarbon base fuel and having dissolved therein a minor amount of an organo-metallic anti-knock agent comprising essentially a reaction product obtained by heating together under pressure an unsaturated aliphatic hydrocarbon and a carbonyl of a metal of atomic number 26 to 28.

3. The motor fuel of claim 2 in which the unsaturated hydrocarbon is an olefin.

4. The motor fuel of claim 2 in which the unsaturated hydrocarbon is a diolefin.

5. The motor fuel of claim 2 in which the saturated hydrocarbon is di-isobutylene and the metal is iron.

' 9. The motor fuel of claim 2' in which the unsaturated hydrocarbon is butadiene and the metal is iron.

10. An aviation motor fuel adapted for use in supercharged engines in super-rich mixtures, which comprises a high anti-knock rating base fuel adapted for use in such engines in lean mixtures, having dissolved therein an organometallic anti-knock agent comprising essentially a reaction product obtained by heating together under pressure an unsaturated hydrocarbon and a carbonyl of a metal of atomic number 26 to 28 in an amount to increase the power output of said fuel at air-fuel ratios below 11/ 1.

11. The motor fuel of claim 10 in which the base fuel comprises aliphatic and aromatic hydrocarbons.

12. The motor fuel of claim 10 in which the base fuel comprises hydrocarbons and a small amount of tetra-ethyl lead.

13. The motor fuel of claim 10 in which the base fuel comprises aliphatic and aromatic hydrocarbons and a small amount of tetra-ethyl lead.

14. The motor fuel of claim 10 in which the base fuel comprises aliphatic and aromatic hydrocarbons, and the reaction product is an iron pentacarbonyl-di-isobutylene reaction product.

PRESTON L. VELTMAN. 

